[jdk21u] RFR: 8338139: {ClassLoading, Memory}MXBean::isVerbose methods are inconsistent with their setVerbose methods

[Goetz Lindenmaier]

A backport to jdk21u as this fixes a jck issue.

 I had to remove the namespace from LogConfiguration::StdoutLog as JDK-8299825 is not in 21.
 I also had to adapt TestVerboseClassLoading, as 'cause' is not known to the logging in 21.

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Commit messages:
 - Fix build and test
 - 8338139: {ClassLoading,Memory}MXBean::isVerbose methods are inconsistent with their setVerbose methods

Changes: https://git.openjdk.org/jdk21u/pull/449/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=449&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338139
  Stats: 204 lines in 6 files changed: 198 ins; 2 del; 4 mod
  Patch: https://git.openjdk.org/jdk21u/pull/449.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/449/head:pull/449

PR: https://git.openjdk.org/jdk21u/pull/449